"A large man wearing black clothes and a backpack, cut open one of the campers' tents with a large knife while he poured some kind of liquid onto the tent," says Police's press spokesman Thomas Fuxborg.
The woman sleeping in the tent sustained minor injuries from the attack and her screaming woke the other campers.
Before fleeing the scene, the suspect set three caravans on fire and hit a man in the head with a baton or a hammer, according to Fuxborg. None of the victims, however, needed medical attention.
The three caravans were completely destroyed in the fire, and a fourth caravan was heavily damaged.
The man is suspected of attempted arson and two cases of assault.
Eleven people lived at the camp site at the time of the attack.